When the 2024 XIX brood of cicada eggs were laid 17 years ago, most Middle Tennesseans were still calling them “17-year locusts”. But they’re not locusts, the blunt headed, orange eyed, clear winged bug is actually a Cicadoidea that can be found in fossilized rocks as far back as 59 million years ago.
Cicadas have wings but they fly like drunken aviators, banging into house walls and tree trunks. The most outstanding feature a cicada possesses is his ability to make noise. In wooded areas, a chorus of thousands of male Cicadas singing their mating calls can be heard by females a half mile away. Their high-pitched singing begins in early morning and increases with the heat of the day to volumes between 85 to100 decibels, which can be as loud as a chainsaw. Many scientists consider the cicada the loudest of all insects, Only the male sings and he does so by flexing his tympanic muscle that causes his tymbal parts to snap against each other, creating a series of clicks that are amplified by air spaces in his abdomen. Those individual clicks are repeated 400 times per second, making it sound to the human ear like a solid noise. As soon as the sun goes down the noisy cicadas go silent until sunrise.
When ground temperature reaches 64 degrees in the spring, periodical cicada nymphs emerge from underground after 13 or 17 years of drinking nourishing fluids from tree roots. The adults shed their exoskeleton and fly into surrounding trees to serenade potential mates with their earsplitting songs. In addition to the periodic 13 and 17-year cicadas, there’s also an annual cicada that stays underground 1 to 5 years and is the one we see every year in Middle Tennessee. The annual cicada is typically larger than the periodic version and has dark green eyes, while the smaller periodic version has eerie reddish-orange eyes.
Periodic cicadas aren’t seen everywhere, but in some forested areas, they may amass in hotspots of up to a million and a half per acre.
After mating, females use their ovipositor to split tree branches and deposit 200 to 400 eggs. In about eight weeks, the eggs hatch and drop to the ground where the larva digs into the earth to find tree roots that will provide food for the next 17 years. Fruit tree farmers usually wait till after the broods die out in late June to plant new trees to prevent female cicadas from splitting young fruit tree limbs to lay eggs that can kill newly planted trees. Normally, old established host trees aren’t permanently damaged by cicadas. Adult cicadas live about a month and subsist by sucking sap from bush and tree limbs with their labrum, which is a lip that’s has evolved to function as a drinking straw.
Cicadas are harmless to humans & pets. They can’t bite because they have no mouth, and they aren’t equipped with stingers. However, their blundering flying skills cause them to occasionally land in the hair of unsuspecting humans, causing a frenzy of swatting and shrieking. Their kamikaze-like habit of flying across highways results in their being splattered on car windshields. Once dried, the cicada entrails require intense scrubbing to remove them from victim vehicles and if not removed, can permanently damage auto paint.
This year the 13 and 17-year cicada broods are emerging simultaneously for the first time since Thomas Jefferson was around. The next time the two broods will emerge together will be in the year 2245.
By Chuck Neese for Friends of Harpeth River State Park.
